<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>js时分秒毫秒倒计时</title>
</head>
<body>
<div>
    <span id="_d">00</span>
    <span id="_h">00</span>
    <span id="_m">00</span>
    <span id="_s">00</span>
    <span id="_ms">00</span>
</div>
<script type="text/javascript">
    function countTime() {
        var date = new Date();
        var now = date.getTime();
        var endDate = new Date("2021-10-01 00:16:00");//设置截止时间
        var end = endDate.getTime();
        var leftTime = end - now; //时间差
        var d, h, m, s, ms;
        if(leftTime >= 0) {
            d = Math.floor(leftTime / 1000 / 60 / 60 / 24);
            h = Math.floor(leftTime / 1000 / 60 / 60 % 24);
            m = Math.floor(leftTime / 1000 / 60 % 60);
            s = Math.floor(leftTime / 1000 % 60);
            ms = Math.floor(leftTime % 1000);

        } else {
            console.log('已截止')
        }
        //将倒计时赋值到div中
        document.getElementById("_d").innerHTML = d + "天";
        document.getElementById("_h").innerHTML = h + "时";
        document.getElementById("_m").innerHTML = m + "分";
        document.getElementById("_s").innerHTML = s + "秒";
        document.getElementById("_ms").innerHTML = ms + "毫秒";
        //递归每秒调用countTime方法，显示动态时间效果
        setTimeout(countTime, 50);
    }

    countTime();
</script>
</body>
</html>